A Content Examination definition analyzes the content of messages, looking for matches you provide. It sets the conditions under which a message is considered safe, or what action should be taken if it isn't. Once configured, each definition is applied to either a Content Examination policy, or Content Examination Bypass policy, to control what message flows it should be used for (e.g. inbound or outbound).

Content Examination definitions shouldn't have to be used to manage inbound emails for spam checking. This is automatically handled by our internal spam scanning software.

Configuring a Content Examination Definition

To configure a content examination definition:

Log on to the Administration Console.

Click on the Administration menu item. A menu drop down is displayed.

Click on the Gateway | Policies menu item.

Hover over the Definitions button.

Select Content Definitions from the drop down menu.

Select a Folderin the hierarchy. You cannot create a definition in the Root folder.

Either click on the:

New Content Definition button to create a definition.

Definitionto be changed.

In the Definition Narrative field, provide a description of the definition. This is kept in the archive for messages that have this definition applied.

Complete the Policy Definitions section as required:

Field / Option

Description

Description

Provide a description of the definition. This is kept in the archive for messages that have this definition applied.

Reference Dictionary: The content is matched against a predefined set of text entries.This option allows you to create a dictionary that can be referenced by multiple content definitions.

Activation Score

Specify a value between 1 and 99 that must be reached before the content definition is triggered. This works by combining the value assigned to text in the "Word / Phrase Match List" field. When the total value of matched text meets this value, the definition is triggered. For example, if the Activation score is set to 6, and there are three words in the "Word / Phrase Match List" field each weighted at 2, and each word appears in the message, the activation score is reached and the definition is triggered.

This field is not displayed if the "Definition Type" field is set to a "Reference Dictionary" value.

Fuzzy Hash Setting

If selected, you can match files that might not be identical, but do hold a configurable level of similarity. Select the appropriate similarity value from the drop down list (80% probability is recommended). A high probability percentage lowers the chances of false positives.

Use the Insert menu item to add a search term. Alternatively, the parameters can be added using the structure in the table below. See the Word Phrase Match List Parameter Details section below for further detail.

Search Parameters

Example

Weight [ :maxscore ] [ search text ]

4:1 “Company Confidential”

Weight [ :maxscore ] [ require ] [ search text ]

1 required “Project X”

Weight [ :maxscore ] [ exclude ] [ search text ]

1 exclude “Tax exemption”

Weight [ :maxscore ] [ regex ] [ regular expression ]

10

Weight [ :maxscore ] [ # ] [ MD5# ]

1 hash 9EBD30E761ED4FF770A90DDBD5CB4190 Confidential.PDF

Both the HTML and TXT parts of a message are treated as separate elements when applying a content examination definition. This means that if a trigger word is present once in a message, but is present in both parts, it scores twice. Similarly if it is present twice in both parts, it scores four times.

Case Sensitive Match

If selected, the entered text entered in the "Word / Phrase Match List" field must match the text case in the message (e.g. uppercase, lowercase, or proper case). If not selected, any case is matched.

This option only applies to standard text search terms.

Match Multiple Words

If selected, a search is performed for repetitions of the text entered in the "Word / Phrase Match List" field. This is used in conjunction with a repetition scoring for the word. For example, an entry of "1:10 notifications" searches for 10 matches of the word "notifications" throughout the message.

Scan Subject Line

If selected, the message's subject is scanned.

Scan Message Headers

If selected, the message's message header is scanned.

Scan Message Body

If selected, the message's message body is scanned.

Scan Attachments

If selected, the message's attachments are scanned. Additionally the "Scan Binary Attachment" and "Microsoft Excel Spreadsheet Scanning" fields are displayed.

Scan Binary Attachment

If selected, documents are scanned for matches based upon the binary data of the file rather than the extracted text content. This option should be enabled for non-text files only (e.g. image / library files).

Enabling this option can increase the number of false positives generated by Content Examination policies.

Raw Files: Scans the file's contents as recorded in the .XLS / .XLSX source file.

Formatted Files: Scans the file's contents as it would be seen by a Microsoft Excel user. This evaluates the formatting of each cell independently, and searches for possible matches across multiple cells.

Complete the Policy Override Options of the "Inbound and Outbound Settings" section as required:

Field / Option

Description

Enable Inbound and Outbound Checks

If selected, the fields / options listed below are displayed. These can be used to protect against unsafe content in both inbound and outbound traffic.

Policy Action

Specify the action to be applied by the definition. The options are:

None: No action is taken.

Hold for Review: The message is sent to the hold queue, and not delivered to the recipients.

Delete: The message is purged from the delivery queue, but retained for auditing purposes. It is referenced as a hard bounce in the message's delivery information. See the Bounced Messages page for further details.

Bounce: The message is rejected, and not delivered to the recipients. A notification is sent with the reason "Message bounced due to Content Examination Policy". See the Bounced Messages page for further details.

Hold Type

If "Hold for Review" is specified as the "Policy Action" field, this option specifies who can see the message via a Mimecast end user application. The options are:

User: Users can see the message in their Personal On Hold view.

Moderator: Moderators can see the message in the Moderated On Hold view. The group of moderators is specified in the "Moderator Group" field.

Administrator: Messages can be viewed by administrators only.

Moderator Group

Specify a group of moderators who can access messages in the Moderated On Hold views via a Mimecast end user application.

Content Preservation (Days)

Specify how long the message remains in Mimecast before being purged. This also applies to messages held in the hold queue once the message expires from the queue.

Leaving both options at 0 (days) doesn't affect the default content retention period set on your account.

Metadata Preservation (Days)

Document Policy

If Document Services is enabled on your account, you can strip metadata from documents before they leave your organization, and convert documents to PDF, ODF, or other Word versions. This option also allows you to apply document services definitions to messages based on their content.

Disable Document Services

Disables Document Services if it is enabled on your account.

Assign to Smart Tag

Assigns a Smart Tag to the message. This field is only available if the "Disable Smart Tags" option is disabled.

Disable Smart Tags

If selected, the ability to add a smart tag to a message is disabled.

Delivery Route

Specify the delivery route to deliver messages to the next mail server. For example, if the message contains the address orders@domain.com, deliver it to the Call Center email server.

If the definition specified in the "Secure Delivery" uses TLS, specify the encryption mode to use. The options are:

Strict: This is a trust enforced mode, and requires a public certificate.

This is the recommended option.

Relaxed Mode: This requires a self signed certificate.

Attachment Strip and Link

If selected, the attachment(s) are removed before the message is delivered. The message contains a notification of the removal in the message's body, and a link is included to download the attachment(s).

Use the Lookup button to send a copy of the message to a group of users.

Stationery Override

Use the Lookup button to apply a Stationery Layout that overrides an existing stationery policy. For example, if the phrase "new product" is in the message, apply a Stationery Layout that promotes the product.

Disable Stationery

If selected, stationery is not applied to any message.

Complete the Notification Options of the "Inbound and Outbound Settings" section as required:

Field / Option

Description

Notify Group

Use the Lookup button to select a group of users to be notified that action must be taken on the message.

Notify (Internal) Sender

Notifies the internal sender, if an outbound message triggers the definition.

Notify (Internal) Recipient

Notifies the internal recipient, if an inbound message triggers the definition.

Notify Overseers

Notifies the Content Overseers to notify them that a message has triggered the definition.

Notify (External) Sender

Notifies the external sender, if an inbound message triggers the definition.

Notify (External) Recipient

Notifies the external recipient, if an outbound message triggers the definition.

When configuring your journal settings, consider our recommended best practice settings. These are based on commonly used configurations, and can provide an optimal solution to protect you against targeted attacks via attachments.

Field / Option

Description

Enable Journal Check

If selected, the fields / options listed below are displayed. These can be used to protect against unsafe content in journaled traffic.

User Mailbox Action

Select the action (or fallback action) to take on the user's mailbox, if a message containing unsafe content is detected. A "User Mailbox Fallback Action" is only applied if we're unable to check a URL.

None: No action is taken on the user's mailbox, and the message is delivered to the recipients.

Remove Message: The message containing unsafe content is removed from the user's mailbox.

In non-Exchange environments automatic remediation is not supported. However if a support journal connector is used, you can leverage detection, and through these alerts perform manual remediation.

User Mailbox Fallback Action

Enable Notifications

Enables a group of users to be notified, as well as the internal sender / recipient, when a message containing unsafe content is found. If selected, the "Notify Group", "Internal Sender", and "Internal Recipient" fields are displayed.

Notify Group

Click on the Lookupbutton, to select a group of administrators to receive notifications of any messages containing unsafe content.

Internal Sender

If selected, a notification is sent to the message's internal sender, if there are any messages containing unsafe content.

Internal Recipient

If selected, a notification is sent to the message's internal recipient, if there are any messages containing unsafe content.

Click on the Save and Exit button.

Word Phrase Match List Parameter Details

Once the words or phrases have been entered into the list "Word / Phrase Match List" field, additional criteria can be added to make the content matching more specific.

The use of formatted file scanning can help reduce the incidence of false positives, but at the risk of missing some content. Content examination of the header and subject of a message is separate from the body examination. However the score is cumulative up to the optional limit. If all sections are selected, all sections are scanned, even if the limit is reached prior to examination of the body / attachments. This is to give the sender a more accurate indication of why their message is not acceptable as per the policy.

Parameter

Description

Weight

The line must begin with the required score for that particular word or phrase.

Maximum Score

Allows you to set the number of occurrences in the message that should trigger the definition. If an entry of 1:10 is added before the search term, Mimecast will match up to 10 instances of the search term. If 1: is entered before the search term, there is no upper limit to the score. This scoring is only used if the option "Match Multiple Words" is enabled. The combined score of the individual Weights is tallied and matched to the Activation Score. The definition is only triggered once the activation score is reached.

Conditions

Allows you to use the operators “required” and “exclude”. Add the word required if the match term is specifically required for the policy to trigger. If a required item is not found, the weight is set to zero and no further scoring takes place. If the word exclude is added after the weight, and the match term does exist, the weight is set to zero and no further scoring takes place. Required and exclude terms should be placed in the first line of the search term list.

Proceed the regular expression with “regex”. Regular expressions can be used to detect structured strings like Social Security Numbers or Credit Card Numbers in emails.

MD5#

Enter the “#” symbol at the beginning of the line (or following the score if relevant) followed by the MD5 code of the attachment. The MD5# is a unique reference given to specific file contents.

If the attachment is known to Mimecast (i.e. Mimecast has previously processed the attachment), this checksum is located in the Transmission Data when viewing the email delivery details.

Preconfigured Reference Dictionaries

Use the Insert | Reference Dictionary menu item to select a Reference dictionary. The entry will begin with the word “reference”, followed by the internal Mimecast reference code and dictionary name. Reference Dictionaries can be created manually, or a predefined Mimecast Managed Reference Dictionary (MMRD) can be selected.

Comments

Comments can be inserted by using a hash symbol (#) at the beginning of the line. These are ignored when examining the message for matches.